1. Field of the Invention
The present invention relates to a printer controller capable of connecting a printer to a plurality of information processing devices having different protocols.
2. Description of the Prior Art:
In an information processing system such as a computer, control information and recording information are transmitted between an output equipment such as a printer, and a host equipment, such as an information processing equipment. Information must be transmitted between the host equipment and the output equipment in accordance with a predetermined protocol which can be decoded by both the host equipment and the output equipment, otherwise the information processing system is unable to function. Accordingly, the protocol of the output equipment, for example, a printer, is prescribed in conformity with the protocol of the host equipment. Therefore, a printer is designed specially for use with a host equipment, or a printer must be equipped with a special protocol converter to be used with a host equipment, when the printer has its original protocol.
In an ordinary protocol converter, a protocol conversion program is operated by the control processor of the printer to convert the control information provided by the host eqiupment into control information represented by the standard protocol of the printer. The converted control information is processed further in the printer to be decoded and converted into internal parameters for controlling the printer.
However, when such a conventional protocol conversion means is employed, the number of protocol conversion programs to be prepared for a printer must correspond to the number of types of host eqiupments to enable the printer to be connected to a plurality of types of host equipments. Accordingly, the number of program steps of the protocol conversion programs increases enormously as the number of types of host equipments to which the printer can be connected increases, whereas only a part of the protocol conversion programs is used in the practical operation of the protocol converter because the printer is connected only to a specified host equipment, which is inefficient in respect of the development of protocol conversion programs and the provision of the protocol conversion programs.
Another possible means is to store protocol conversion programs corresponding to the types of host equipments to which the printer can be connected in read only memories (ROMs) and to mount a ROM storing a specific protocol conversion program for a specific host equipment on the protocol converter when the printer is assigned to the specific host equipment. However, this means requires the same efforts for developing the protocol conversion programs as the foregoing means and requires labor and expenses for producing ROMs for storing the protocol control programs. Thus, it has been inefficient to enable a single output equipment such as a printer to be connected to a plurality of types of host equipments.